[Feature] - Extract instruments from PMD .M/.M2 file about ym2608-tone-editor

[OPNA2608]

I think it's doable to some degree. There are some older versions of PMD modules / modules compiled with unusual options where this code might not apply but awhile ago I hacked something together which sort-of worked: https://github.com/OPNA2608/libopenpmd/blob/436af496988b909b57694d12165a941996b2fb20/src/tools/pmd_instrip.c#L122-L179

• 0x0000 needs to be 0x00 for PC-98 platform, otherwise the next pointer is most likely wrong. (not investigated much)
• 0x0019 has a short with an offset relative to the platform byte (add +1 for absolute offset in file) to the instrument definitions section.
• The instrument definitions section is a list of instrument ID -> register data mappings. The format of the latter is equivalent to the .FF file format's register data (just the register stuff, without the instrument name). This list is terminated by a 0xFF00 short. (Or 0x00 ID + 0xFF first register value if you want to detect it that way)

[rerrahkr]

Added at c49475c, thank you for your information!